Pruning grape vines in Minnesota
Time: 8:04 | Covers basic pruning for northern climate: definitions of trunk, cordons, shoots, head, canes, and spurs; training shoots to a trellis to form a cordon; counting buds to know where to cut; controlling fruit load and sun exposure.
[Tom van der Linden]: It's spring in Minnesota, a great time to prune grape vines. Proper pruning of grape vines means better grapes. And better grapes mean better wine. We'll cover basic pruning for a northern climate. For details on how to prune for your climate, check with your state university extension.
Year one, we take the initial shoot and we train it into a trunk. Year two, we pick two healthy shoots and we train them to our trellis. We'll take the two healthiest shoots and train them on the trellis to form a cordon. We'll prune off the other shoots leaving just the trunk and the cordons. To review quickly, our first shoot we train into a trunk in year one, then in year two we take our two best shoots and we train them to the trellis to make cordons. Year three, the trunk of our vine is gaining strength and circumference. We have cordons that are now trained to a trellis and off each cordon we have new shoots.
Toast yourself, you've learned three new terms. We have trunk, cordon and shoot. Now we'll learn three new terms, and then we'll move on.
The top of a trunk where it stops is called the head of the vine, and this vineyard for this particular grape the head is about four feet off the ground. You'll see vineyards where the head is higher or lower depending on the use of the grape, the kind of trellis they're using. So it'll be okay to have different heights.
In spring, a new green shoot grows from our cordon. And now after the leaves have fallen in the fall, the shoot becomes a cane. For spring pruning, we're going to take last year's cane, and when we clip it again, it will become a spur.
Working on a little older vine, here's the head and the nice, thick trunk. We have a cane, and then a spur, and then a cane, and then a spur. Don't worry, you'll soon get the hang of it.
Taking a close-up look, we have the cordon here, and we have a shoot from last year coming off and we need to shorten the shoot now in spring to make a spur... so that we can control our fruit load. Let's count buds: we have a bud here, we have a bud here, we have a bud here, and we have a bud here, and so forth. On some varieties, this bud close to the cordon is not fruitful so we won't count those buds. We'll count first a bud here and a bud here and make our cut out here. In other varieties we will need to count this bud as one, two, and we'll make our cut here. Whatever you do, you'll want to keep good records so when you go back into your vineyard you can see how the fruit responded to your pruning.
So let's count the buds on this cane. We have one, two, three buds, and we're looking for two. So we have one bud, two buds, and we clip there.
We need to prune this vine to control both the fruit load and the sun exposure. It's important in a northern climate to get good sun exposure on your grapes so that they ripen fully. This is a Frontenac vine that's growing on the cordons are growing along the upper trellis wire. So let's estimate the fruit load on this particular vine. We have seven fruiting spurs on each cordon, and each spur has two buds. Now each bud will produce two clusters of grapes. We can look up the grape variety we're growing and we can find out what an average cluster will weigh. In this case, they will weigh about four ounces.
First, simply convert pounds of grapes to ounces. Next, divide number of ounces by the number of ounces in a cluster to get the number of clusters. Once you know the total number of clusters, figure out the total number of buds. Finally, convert the number of buds to number of spurs. That's it!
Don't worry, you'll have time to review. And if you make a mistake, it'll still turn out just fine. So why go to all this trouble? Well remember, we want to get good sun exposure on our grapes, and we want to balance the fruit load on our vine so we don't overtax our vine.
For more on selecting, growing, and caring for grape vines in the upper Midwest, see these sources of information.